Adding and subtracting strategies

Adding and subtracting strategies: I can add and subtract in my head and in columns, and check my answers.

1. 54 + 23. Start at 54. Partition 23: split it into 20 and 3.

   Hop on the tens first: 54 + 20 = 74.

   Then hop on the ones: 74 + 3 = 77.

   54 + 23 = 77

   Picture: A number line from 50 to 80, labelled every 10. A dot at the 4th tick after 50 labelled "54". The frog hops from the 4th tick after 50 to the 4th tick after 70 (+20), then to the 7th tick after 70 (+3).

2. 53 − 7. Start at 53. Bridge through ten: stop at 50 on the way.

   Hop back 3 to reach 50: 53 − 3 = 50.

   7 is 3 and 4, so hop back 4 more: 50 − 4 = 46.

   53 − 7 = 46

   Picture: A number line from 40 to 60, labelled every 10. A dot at the 3rd tick after 50 labelled "53". The frog hops from the 3rd tick after 50 to 50 (−3), then to the 6th tick after 40 (−4).

3. Your turn: 62 − 5. Start at 62. Bridge through ten: stop at 60 on the way. What is 62 − 5?

   Picture: A number line from 50 to 70, labelled every 10. A dot at the 2nd tick after 60 labelled "62".

   Choose one:

   • 55
   • 57
   • 60

   Answer

   The answer: 57

   62 − 2 = 60. Then 60 − 3 = 57.

   Picture: A number line from 50 to 70, labelled every 10. A dot at the 2nd tick after 60 labelled "62". The frog hops from the 2nd tick after 60 to 60 (−2), then to the 7th tick after 50 (−3).

Words to know